Boiler installation and method of operation



Jully Q3, g.; K, TOENSFELDT 2,@@723 BOILER INSTALLATION AND METHOD OF OPERATION Filed Nov. 2, 1932 2 Sheets-Sheet 2 I i* j e j ATTORNEYS Patented July 9, 1935 BOILER INSTALLATION METHODtOF OPERATION 4 Kurt Toensfeldt, Port Washington, N. Y., assignor to International CombustionEngineering Corporation, New York, N. Y., a corporation of Delaware Application November 2, 1932, Serial No. 640,735

" 4 claims. (cl.l 122-235) This invention relates to boiler installations and method of operation, and is particularly useful where a superheater, azreheater and an air heater are employed. Y I

The nature and objects of the invention wil be understood from the following: In present practice in high capacity boiler installations, superheats and reheats rise as high as 800 to 825 F., requiringv a full ilow of gas over the super-` heater'and the reheater. YDue to the overheating which occurs at high rates, it is Anecessary Ato by-pass some of the gas in order to hold the superheat or the reheat down to normal,` this being desirable not only'from the standpoint of erlif ciency but from thestandpoint of the life of the superheater and the reheater tubes.

It has been known to by-pass gasin such installations, but I `propose to accomplish this in a manner whereby a maximum-sized air heater, required for eflicient` operation of the unit, may be employed; whereby the by-passed gas mingles with the gas leaving the reheater at approximately the same temperature instead of atA markedly diiferent temperatures 'which isunde sirable; Vand whereby the amount of convection surface needed to properly'cool the by-passed gas is small and makes foran economical arrangement of parts. Also by my invention the unit may handle slightly more flue gas per unit lfor the same temperature of gas entering the air heater with consequent increase in steam output and increase in efficiency, as compared to installations'in which no by-passed gas is passed ovei` convection surfaces.

I-Iow the foregoing, together with such other obj ects and advantages as may hereinafter appear or are incident to my invention, are realized is illustrated in preferred form in the accompanying drawings, wherein-V Fig. 1 is a vertical section through a boiler installation embodying my improvement, and

Fig. 2 is a section taken on the line 2-2 of Fig. 1.

In the combination of parts constituting my improved installation Iprovide a boiler the tubes of which are arranged in the form of a six-sided box to provide a combustion chamber A. The boiler has an upper steam and water drum 1 and a mud drum 8 therebelow, the tubes dening the combustion space being connected so as to receive their Water supply from the mud drum and to deliver into the steam and Water drum. At the rear of the combustion chamber a baille 9 is associated with the tubes defining the rear wall of the combustion chamber, said baille extending upwardly from the drum 8 to a point short of the steam and water drum 'I. Abo-ve the spaced tubes I which are at the top of the combustion chamber is a space B for the superhe'ater II. Horizontal baille `means I2 are associated With the tubes I0 and the baille 9 so as to normally direct all of the gaseous products of combustion leaving the combustion space over the superheater II. Forming part of the baffle I2is a damper I3 operated in any preferred mannerl `from the exterior of the setting and by which a portion of the gases maybe by-passed around the superheater. The side wall tubes I4 are carried upwardly to line thel sides of the space in which the superheater is located, this space being further lined at the top by the tubes I5 which connect with the steam and Water drum I and constitute the delivery tubes for the side wall tubes I4. The tubes I0 at their rear portion rise upwardlyfor connection with the steamv and water drum l. Thus the superheater is `bounded on ve sides by evaporating tubes which tend to prevent overheating and maintain the superheater normal, except at periods of high rating when the damper I3 is opened in an amount suflicient to by-pass enough gas to prevent rise in superheat above normal. Spaced apart from the few tubesV with which the baffle 9 is associated, is a group or bank of convection tubes I6,` the number of which is small, these tubes constituting the downcomers from drum 'I to drum 8. With the rear tubes of the bank` I6 is associated a baille I'I, this baille extending short of the steamand water drum in order to permit ilow of gases from the superheater space into the oiltake C in which the reheater elements I8 are located. Bailles I9, preferably three in number, extend rearwardly from the baffle 9 to the front tubes of the bank of tubes I6 and at the lower end of the baille II there is a damper 20 controlling the outlet passage 2l at the bottom of the bank of tubes I 6.

The damper 20 is normally closed, but under conditions of operation when there would be a tendency for the temperature of reheat to rise above normal, the damper 20 is opened to an extent suincient to Icy-pass the required amount of gas to maintain normal reheat temperature. Gas will by-pass upon opening of the damper 2D because the resistance to flow through the bank of tubes I6 is less than that through the reheater elements. The amount of convection surface presented by the convection bank of tubes I 6 is, therefore, approximately just sufcient to lower the temperature of the gases which leave the bank to the temperature of the gases leaving the reheater elements at normal temperature for reheat. The gas is, therefore, mingled at the same temperature.

The air heater 22 is of maximum size to give the nal exit temperatures of the gas, and thus it will be seen that the amount of convection surface in the bank of tubes I6 does not have to be unduly'large-in fact no larger than that required to lower the temperature of the by-passed gas to that of the gas leaving the reheater. Thuseconomy and eiliciency not only from the standpoint of the air heater, but also from the standpoint of the convection bank of tubes, are obtained. It is much more economical to provide convection surface by way of air heating surface than it is by way of providing convection boiler tubes. In addition it will be seen that the arrangement of convection tubes is simple and economical, and because of the small number, adequate ligament eiliciency can be Obtained and the installation operated on high pressures. The use of a radiant heat boiler also makes it possible to reduce the amount of convection surface over that which would otherwise be required.

I prefer to so proportion the various surfaces,- save at periods of higher rating, when there is va tendency to over superheat and over reheatto secure the following gas temperatures; leaving the furnace 18l0; entering the superheater 1720; leaving the superheater 1305"; entering the reheater 1l85; leaving the reheater 775. The installation as shown is calculated to operate on pressures of 1400 pounds. l

I claimz- 1. In combination, an upper steam and water drum, a mud drum therebelow, boiler tubes defining combustion space for the boiler connected for supply and delivery to said drums respectively, a superheater above the combustion space, there being but few boiler tubes interposed between said superheater and said combustion space, means for by-passing a portion of thev superheater, a reheater therein, al bank of convection tubes connecting the drums, means providing a pass for said convection tubes in parallel with the reheater for gas flow and which offers less resistance to gas ow than that of the reheater, a substantially full sized air preheater serially `following the reheater, and a damper controlling the pass of the convection bank, the

amount of surface presented by the convection bank being suflicient to reduce the temperature of the by-passed gases approximately to that of the gases leaving the reheater.

2. In combination, a furnace-shaped boiler, a superheater in an upper portion of the boiler over which products of combustion pass in leaving the combustion chamber of the boiler, a gas offtake joining the boiler adjacent the superheater, adjustable means for by-passing gases around the superheater to the oitake, a pair of oiftake passages having their entrance ends both adjacent said point', an additional oitake passage into which said pair of passages deliver, an air heater in the additional passage, a steam heater in one passage of said pair, boiler tubes in the other passage of said pair, the boiler tubes being arranged to offer less resistance to gas flow than the steam heater, and adjustable means for controlling the flow of gases through the passage containing the boiler tubes.

3. In combination, a furnace shaped boiler having a combustion chamber at least in large part defined by tubes providing the major prtion of the heat absorbing surface ot the boiler proper, convection tubes also associated with said boiler, a gas oitake disposed beyond the major portion of the boiler with respect to gas flow, the offtake including a pair of passages arranged in parallel with respect to gas flow in an advance portion of the oftake,said offtake further including an additional passage into which said pair of passages deliver, an air heater in said additional passages, a reheater in one passage of said pair, said convection tubes being located in the other passage of said pair, and means for controlling now of gases through the passage containing the convection tubes.

,4. The. method of operating a boiler installation having an oiftake with a reheater in an advance portion thereof and an air heater in a succeeding portion thereof, and further having a by-pass around said reheater with convection surfaces therein; which method includes passing substantially all of the gases through the reheater at substantially normal ratings and, at higher than normal ratings, passing gases through said by-pass in amounts such as to maintain the rcheat temperature substantially the same as for the normal ratings, so as to reduce the by-passed gas temperature approximately to that of the gases leaving the reheater.

KURT TOENSFELDT. 

